fn try_build_engine(model: &Model) -> Result<(Option<Engine>, Snapshot), String>Expand description
Build a live engine over every enabled derived measure in model,
propagating a build failure (cycle, type/dimension error) instead of
swallowing it. A measure whose formula is disabled (DISABLED_MARKER) is
excluded, via engine_model.
Ok(None) (no engine, successfully) when nothing is left to compute — a
model with no derived measures, or one whose formulas are all disabled.